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Some Derivative Error
Posted 2011年1月24日 GMT-5 04:16 1 Reply
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Hello everyone,
I've been working on a certain model in COMSOL 4.0, and when I try to solve the whole model, I receive this error:
Failed to evaluate expression.
- Expression: d((mod1.cn.crosswind)*(dvol),{test@3})
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.cn.crosswind@VDN${test@3}
- Defined as: ((((((mod1.cnz-((1/nojac(max(((mod1.cn.w^2)+(mod1.cn.u^2)),sqrt(eps))))*((mod1.cnz*nojac((mod1.cn.w^2)))+(mod1.cnr*nojac((mod1.cn.u*mod1.cn.w))))))*abs(mod1.cn.Res cn)))*((2*mod1.cn.cwdhv1 cn)*mod1.cn.cwdhv2 cn))*pi)*r)
Failed to evaluate variable.
- Variable: mod1.cn.cwdhv1 cn
- Defined as: (-0.5*nojac(max(0,(if((gmg level==0),0.40000000000000002,0.69999999999999996)-(((mod1.cn.Dav cn*2)*sqrt(emetric(mod1.cnr,mod1.cnz)))/max(abs(((mod1.cnz*mod1.cn.w)+(mod1.cnr*mod1.cn.u))),((emetric2^0.25)*(mod1.cn.Dav cn*mod1.cn.glim))))))))
Failed to evaluate expression.
- Expression: nojac(max(0,(if((gmg level==0),0.40000000000000002,0.69999999999999996)-(((mod1.cn.Dav cn*2)*sqrt(emetric(mod1.cnr,mod1.cnz)))/max(abs(((mod1.cnz*mod1.cn.w)+(mod1.cnr*mod1.cn.u))),((emetric2^0.25)*(mod1.cn.Dav cn*mod1.cn.glim)))))))
Failed to evaluate variable.
- Variable: mod1.cn.glim
- Defined as: ((unit mol cf*0.10000000000000001)/((unit m cf^3)*chds.helem))
Failed to evaluate variable.
- Variable: chds.helem
- Geometry: 1
- Domain: 1 2 3 4 5
I think it has something to do with derivatives in my model, but I'm not sure... Can you please help me out? :)
I've been working on a certain model in COMSOL 4.0, and when I try to solve the whole model, I receive this error:
Failed to evaluate expression.
- Expression: d((mod1.cn.crosswind)*(dvol),{test@3})
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.cn.crosswind@VDN${test@3}
- Defined as: ((((((mod1.cnz-((1/nojac(max(((mod1.cn.w^2)+(mod1.cn.u^2)),sqrt(eps))))*((mod1.cnz*nojac((mod1.cn.w^2)))+(mod1.cnr*nojac((mod1.cn.u*mod1.cn.w))))))*abs(mod1.cn.Res cn)))*((2*mod1.cn.cwdhv1 cn)*mod1.cn.cwdhv2 cn))*pi)*r)
Failed to evaluate variable.
- Variable: mod1.cn.cwdhv1 cn
- Defined as: (-0.5*nojac(max(0,(if((gmg level==0),0.40000000000000002,0.69999999999999996)-(((mod1.cn.Dav cn*2)*sqrt(emetric(mod1.cnr,mod1.cnz)))/max(abs(((mod1.cnz*mod1.cn.w)+(mod1.cnr*mod1.cn.u))),((emetric2^0.25)*(mod1.cn.Dav cn*mod1.cn.glim))))))))
Failed to evaluate expression.
- Expression: nojac(max(0,(if((gmg level==0),0.40000000000000002,0.69999999999999996)-(((mod1.cn.Dav cn*2)*sqrt(emetric(mod1.cnr,mod1.cnz)))/max(abs(((mod1.cnz*mod1.cn.w)+(mod1.cnr*mod1.cn.u))),((emetric2^0.25)*(mod1.cn.Dav cn*mod1.cn.glim)))))))
Failed to evaluate variable.
- Variable: mod1.cn.glim
- Defined as: ((unit mol cf*0.10000000000000001)/((unit m cf^3)*chds.helem))
Failed to evaluate variable.
- Variable: chds.helem
- Geometry: 1
- Domain: 1 2 3 4 5
I think it has something to do with derivatives in my model, but I'm not sure... Can you please help me out? :)
1 Reply Last Post 2011年1月24日 GMT-5 05:22
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Posted:
1 decade ago
Hi
you are right, the Newton solvers need a derivative.When COMSOL has problems to identify the derivative, it often comes from step functions on BC's or initial values not well defined producing step functions that are not really integrable. Check your BC and initial conditions, the isue might be there
--
Good luck
Ivar
you are right, the Newton solvers need a derivative.When COMSOL has problems to identify the derivative, it often comes from step functions on BC's or initial values not well defined producing step functions that are not really integrable. Check your BC and initial conditions, the isue might be there
--
Good luck
Ivar